Circle polishing aluminium

[slotalot]

I had a try at this some years ago - the bit that I made was only about 3 inch square and not for a slot machine. I used discs of cork stuck to the end of a turned down dowel rod, (bit of brush handle) in a drill stand. The cork discs were meant to be used as feet on craft items (you can get them at B&Q type shops). What I did notice was that if you use a drill stand, you are limited by the depth from the centre of the chuck to the pole on the stand , so you would struggle with a full backplate due to the size. The results were "OK" but could have been better.

I have just found this on Youtube, that might help:

[gameswat]

Here's some pics of a rough Circle Skill I restored about 5 years ago... At the time I didn't have a mill so just used my floor standing drill press. I cut a small circle of 3M pot scouring material and glued it to a circle of wood the right dia with a bolt through it for a shank. The circular pinfield was easy enough but as the playfield was larger it only just fit my press by moving the playfield sheet 180 degrees around to get all the turning onto it. By looking closely at Bollands old photo I could see that while the horizontal lines of engine turning where dead straight, the vertical lines were actually a little wonky. So that wasn't done on a mill, but was turned using a drill press only and by hand! It was quite simple, I just clamped a straight length of wood to my drill table at the correct spacing to act as a stop for the top edge of my playfield sheet. Then just using my eyesight as a guide, I carefully turned each circle. From memory the next circle is about 2/5ths over the previous one. Then, when I'd finished the first horizontal line, I unclamped the wood and moved it the correct amount for the next line. The only way you notice the slight wonkyness of it is to look at an acute angle from the top or bottom, then you can see it's hand done, but as I wanted it authentic that's perfect anyway! ...Well worth the effort I think, so good luck!

[gameswat]

I also restored this very ratty coin payout Circle Skill a number of years ago... I wish I'd polished away some of the machine turning on my restored cig model playfield to make it look a little aged, oops.

One thing I remembered about my polishing after watching the posted video clip of DIY engine turning for the model airplane is, it was actually a more industrial form of 3M scouring material I used. This was cut from a burnishing wheel pad used on a polishing wheel/bench grinder. You use these to burnish stainless steel or remove rust/paint. A lot tougher than the green 3M pot scouring material.

[gameswat]

Was restoring the playfield of a Bradley Challenger the other night so decided to film a short clip showing how quick the machine turning is once set up.



Again, used a piece of 3M burnishing wheel cut down to fit, then glued onto a new Dremel-style grinder wheel that was the right diameter. This time I found using a spray metal cutting oil on the surface made a huge improvement! As it stops the alloy clogging the scouring material and makes a more uniform circle. I also marked the length of wood that acts as a stop. With the metal sheet marked along the top edge in several places as well, I was able to quickly move the sheet forward each time the exact same amount, so the circles are uniformly spaced. Once a line is finished, it's just a mater of moving the wood stop back the same amount, in this case 15mm. Then starting another line, but this time offsetting the circles by half, I just positioned the alloy sheet in the middle of the marks on the measured wood stop. In fact this is much improved over the spacing on both machines originally - they were actually both quite different in size and spacing and pretty average quality at best. I lightly rubbed the finished sheet with fine steel wool once the pins were replaced to age it slightly, as it looked too new otherwise, compared to the worn outer plating and original varnish. Will wear quickly with testing I'm sure from sharp edged coins too.

I was looking around the net and apparently there is a plastic rod in various diameters sold that's impregnated with cutting compound and used for engine turning. Would be easy enough to cut the diameter down too if the size wasn't right. I read a supplier was the Eastwood Company in the USA, but couldn't find it on their site, maybe different wording is needed?

[gameswat]

Here's a close up of the burnishing wheel I cut up to use and the tool. In fact when I removed this from the press I noticed it had mushroomed somewhat, (reshaped in this photo), so my circles were slightly larger diameter than I'd planned. I left it long as was expecting wear to the burnishing head as normally happens, but with cutting oil there was no wear at all. So for the next one I'll shorten the burnishing head a little to stop that mushrooming so much.